ci: add GitHub Actions test workflow

.github/workflows/tests.yml

@@ -0,0 +1,34 @@
+name: tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.11", "3.12"]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: pip
+      - name: Install
+        run: |
+          python -m pip install --upgrade pip
+          # symfluence is a runtime import of the calibration worker and plugin
+          # registration but is not declared in pyproject (the pure-JAX model runs
+          # without it); install it explicitly so those tests can execute.
+          pip install symfluence
+          pip install -e ".[jax,dev]"
+      - name: Run tests
+        run: pytest -q